North Carolina officials are warning more residents who live near Duke Energy's coal ash pits that it's not safe to drink or cook with their well water after tests showed contamination levels that raised concerns.

The state Department of Environment and Natural Resources said Tuesday that 152 wells tested near Duke's dumps failed to meet state groundwater standards. That represents more than 93 percent of the 163 wells for which tests have been completed so far.

Advertisement

Many of the tests results show high levels of such toxic heavy metals as lead, vanadium and hexavalent chromium. Duke has suggested the contamination could be naturally occurring.

A law passed after last year's spill into the Dan River required testing of all drinking wells within 1,000 feet of Duke's 32 coal ash dumps.